As techniques for fluorinating compounds containing C—H bonds by converting all the C—H bonds to C—F bonds, use of cobalt trifluoride, direct fluorination with fluorine gas and electrochemical fluorination using hydrogen fluoride electrolytically obtained from electrolytic cells as the fluorine source (hereinafter referred to as ECF) have been known.
These fluorination techniques are applied to give various useful fluorinated compounds. As an example of production of fluorinated acyl fluorides highly useful as intermediates of fluorinated compounds by ECF, production of perfluoroacyl fluorides by ECF of partially fluorinated esters obtained from primary or secondary alcohols and fluorinated acyl fluorides followed by dissociation of the resulting perfluoroesters is disclosed (U.S. Pat. No. 3,900,372). Liquid phase fluorination in which a hydrogen-containing organic compound dispersed or dissolved in a perhalogenated liquid medium is fluorinated with fluorine gas blown into the medium is disclosed as a fluorination method using direct fluorination (U.S. Pat. No. 5,093,432 and JP-A-4-500520).
However, use of ether oxygen-containing compounds as the substrate in synthesis of fluorinated acyl fluorides by ECF has a problem of very low yields due to cleavage of the C—O bonds. Use of ether oxygen-containing compounds containing no fluorine atoms as the substrate in liquid phase fluorination also has problems of poor yields of fluorinated products and poor volume efficiency.
The present invention aims to solve the problems with the prior art and provides a production process which permits efficient fluorination, even if the substrate is an ether oxygen-containing compound, with a high yield of fluorinated acyl fluorides. The present invention also provides a process for industrially preparing fluorinated acyl fluorides by employing ether oxygen-containing compounds having a specific structure. Further, the present invention provides a process for preparing fluorinated vinyl ethers useful as starting materials for fluororesins.